[openstack-dev] [Mistral][Zaqar] Triggering Mistral workflows from Zaqar messages

Zane Bitter zbitter at redhat.com
Wed May 18 18:49:31 UTC 2016

I've been lobbying the Mistral developers for $SUBJECT since, basically, 
forever.[1][2][3] I like to think after a couple of years I succeeded in 
changing their view on it from "crazy" to merely "unrealistic".[4] In 
the last few months I've had a couple of realisations though:

1) The 'pull' model I've been suggesting is the wrong one, 
architecturally speaking. It's asking Mistral to do too much to poll 
Zaqar queues.
2) A 'push' model is the correct architecture and it already exists in 
the form of Zaqar's Notifications, which suddenly makes this goal look 
very realistic indeed.

I've posted a Zaqar spec for this here:


Not being super familiar with either project myself, I think this needs 
close scrutiny from Mistral developers as well as Zaqar developers to 
make sure I haven't got any of the details wrong. I'd also welcome any 
volunteers interested in implementing this :)

One more long-term thing that I did *not* mention in the spec: there are 
both Zaqar notifications and Mistral actions for sending email and 
hitting webhooks. These are two of the hardest things for a cloud 
operator to secure. It would be highly advantageous if there were only 
_one_ place in OpenStack where these were implemented. Either project 
would potentially work - Zaqar notifications could call a simple, 
operator defined workflow behind the scenes for email/webhook 
notifications; alternatively the Mistral email/webhook actions could 
drop a message on a Zaqar queue connected to a notification - although 
the former sounds easier to me. (And of course clouds with only one of 
the services available could fall back to the current plugins.) 
Something to think about for the future...


[2] http://lists.openstack.org/pipermail/openstack-dev/2015-May/063884.html
[3] Also in-person at every summit since at least Juno :)
[4] http://lists.openstack.org/pipermail/openstack-dev/2015-May/063904.html

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